The invention pertains to stabilizing fins for use with watercraft. More particularly, the invention relates to movable fins for use with surfboards, windsurfers, kite surfers and boats.
Various designs for fins, both fixed and movable have been developed for use with surfboards and other watercraft. Movable fins provide allow for enhanced directional guidance associated with multiple fin systems while permitting reduced water resistance during turns. U.S. Pat. No. 6,053,789 issued to Miyashiro discloses a limited pivotal fin system for a surfboard. The system includes an upper stationary mounting portion attached to the underside of the surfboard, and a lower pivoting fin with a limited rotational pivoting mechanism located in an upper recessed area on the leading edge of the pivoting fin.
U.S. Pat. No. 4,811,674 issued to Stewart, describes a foil arrangement for water-borne craft in which the hull of the watercraft includes a pair of tiltable foils disposed at the stern of the craft at either side of the centerline. The foils tilt outwardly when the watercraft is moving straight ahead, causing the rear of the craft to lift, thus reducing hydrodynamic drag and increasing speed. The foils tilt downwardly and inwardly in turns, acting as an extra fin and serving to tighten the turn of the watercraft.
U.S. Pat. No. 4,854,904, issued to Wahl discloses a sailboard with an adjustable keel mechanism. The keel is capable of pivoting about a vertical axis located rearwardly from the center of the keel. The keel is forced by the flow of oncoming water to rotate in the windward direction from its centered position. A spring-loaded detent may be employed to return the keel to its centered position.
U.S. Pat. No. 4,733,496 issued to Wallner illustrates a pivoting surfboard fin that includes a rudder-like section that swings out when a turn is commenced, enhancing the maneuverability of the surfboard by redirecting the water flow through the pivoting rudder section in the direction of the turn. The fin employs a spring-loaded pin traveling in a tapered channel, which channel is deepest at the centerline of the fin, to center the rudder-like section of the fin.
U.S. Pat. No. 3,890,661 issued to Johnson discloses a surfboard rudder-fin combination that permits the surfer to vary the angle of the fin with respect to the surfboard by shifting his weight on the board. A spring-loaded lever arm is employed to control the degree of rotation of the fin. While other variations exist, the above-described designs for movable watercraft fins, rudders and foils are typical of those encountered in the prior art.
It is an objective of the present invention to provide a fin system for watercraft that will permit tighter turning and improve maneuverability of the craft by providing at least one fin that will resist maneuvering forces while permitting an opposing fins to xe2x80x9cfeatherxe2x80x9d or turn so as not to oppose the oncoming flow, thus minimizing drag from inactive fin. It is a further objective to provide a system that avoids unnecessary drag when the watercraft moves in a downwind direction by permitting fins on either side of the watercraft to automatically assume an orientation that minimizes resistance to the water flow beneath the craft. It is yet a further objective to permit the user of the system to adjust the limits of the arc through which the fin may rotate. It is still a further objective to enhance the ability of wind-powered watercraft to move in an upwind direction. Finally, it is an objective of the invention to provide the above-described capabilities in an inexpensive and durable fin system that may be easily cleaned of sand and debris and that may be easily repaired and maintained.
While some of the features of the present invention are disclosed in the prior art, none of the inventions found satisfy all of the requirements identified.
The present invention addresses all of the deficiencies of prior art fin and watercraft inventions and satisfies all of the objectives described above.
A fin and watercraft system providing the desired features may be constructed from the following components. A watercraft is provided. The watercraft has a front end, a rear end, a midpoint between the front end and the rear end, a lower surface, an upper surface, first and second sides and a centerline between the first and second sides. At least one pair of fins is provided. The pair of fins includes a first side fin and a second side fin. The pair of fins is located between the midpoint and the rear end of the watercraft, equidistant from the centerline and equidistant from the rear end.
The first side fin is located adjacent the first side of the watercraft and the second side fin is located adjacent the second side. Each of the first and second side fins has a top end, a bottom end, a leading edge, a trailing edge and a vertical axis. A horizontal axis extends from the leading edge to the trailing edge of the fin. A front portion of the fin extends from the leading edge to the vertical axis. A rear portion of the fin extends from the vertical axis to the trailing edge. The fin includes and first and second lateral surfaces. Each of the first and second side fins is rotatably mounted about the vertical axis to the lower surface of the watercraft. The first side fin is rotatable from a first position to a second position. The second side fin is rotatable from a third position to a fourth position.
When the watercraft is forced to move in a direction parallel to its centerline, an oncoming flow of water beneath the watercraft will cause the first side fin and the second side fin to rotate to the first and third positions, respectively. When the watercraft is forced to move in a direction from the centerline toward its first side, the oncoming water flow will cause the first side fin to rotate to the second position and the second side fin to remain in the third position. When the watercraft is forced to move in a direction from the centerline toward its second side the oncoming water flow will cause the second side fin to rotate to the fourth position and the first side fin to remain in the first position.
In a variant of the invention, when the first side fin is located in the first position its horizontal axis is parallel to the centerline of the watercraft. When the second side fin is located in the third position its horizontal axis is parallel to the centerline of the watercraft. When the first side fin is located in the second position its horizontal axis is angled toward the centerline at between zero and ninety degrees to a position of the horizontal axis when the first side fin is located in the first position. When the second side fin is located in the fourth position its horizontal axis is angled toward the centerline at between zero and ninety degrees to a position of the horizontal axis when the second side fin is located in the third position.
In a further variant, when the first side fin is located in the first position its horizontal axis is angled toward the centerline of the watercraft at a fixed angle between zero and fifteen degrees. When the second side fin is located in the third position its horizontal axis is angled toward the centerline of the watercraft at a fixed angle between zero and fifteen degrees. When the first side fin is located in the second position its horizontal axis is angled toward the centerline at between zero and ninety degrees to a position of the horizontal axis when the first side fin is located in the first position. When the second side fin is located in the fourth position its horizontal axis is angled toward the centerline at between zero and ninety degrees to a position of the horizontal axis when the second side fin is located in the third position.
In yet another variant of the invention, the rear portion of each of the first and second side fins is larger than the front portion of the fins, causing the fins to rotate so as to align with a flow of oncoming water.
In still another variant, the first lateral surface of each of the first and second side fins is symmetrical to the second lateral surface of each of the first and second side fins.
In still a further variant, a circular rotational portion is located at the top end of each of the fins. The rotational portion has a top surface and a bottom surface. The top surface is at right angles to the vertical axis and has a first circular bearing track adjacent a perimeter of the top surface. The first circular bearing track has a first diameter and a first width. An axle is provided. The axle has a first end and a second end and is fixedly attached to the fin at the second end and extends upwardly through the vertical axis. The axle has an attaching means located at the first end. A securing means is provided. The securing means is sized and shaped to engage the attaching means at the first end of the axle.
A circular bearing plate is provided. The bearing plate has a central orifice and is sized to slidably accommodate the axle. The bearing plate has an upper surface and a lower surface. The lower surface has a second circular bearing track of the first diameter and of the first width adjacent to a perimeter of the bearing plate. The second bearing track is sized and shaped to fit slidably against the first bearing track.
A bearing is provided. The bearing has an outer shell and an inner sleeve. The sleeve is slidably rotatable within the outer shell, the outer shell is fixedly mounted to the upper surface of the bearing plate above the central orifice. The inner sleeve is attached to the axle such that the axle cannot rotate with respect to the sleeve. Means are provided for limiting rotation of the fin with respect to the bearing plate.
A recess is provided. The recess extends upwardly from the lower surface of the watercraft and is sized and shaped to accommodate the first end of the axle, the attaching means, the circular bearing plate, the bearing and the top surface of the circular rotational portion of the fin. Means are provided for attaching the bearing plate within the recess such that the bearing plate does not rotate with respect to the watercraft and the top surface of the circular rotational portion of the fin is maintained at a level of the lower surface of the watercraft.
When the first end of the axle is extended through the orifice in the bearing plate and secured to the inner sleeve of the bearing, the first bearing track is fitted slidably against the second bearing track, the securing means engaging the attaching means at the first end of the axle and the bearing plate is secured to the recess, the fin will be rotatably attached to the lower surface of the watercraft.
In another variant of the invention, the first and second lateral surfaces join the bottom surface of the circular rotational portion of each of the first and second side fins in a radius, thereby increasing the resistance of each of the fins to lateral forces.
In still another variant, a first ball bearing race is provided. The first ball bearing race extends upwardly from the first circular bearing track and is sized and shaped to fit slidably a series of ball bearings of a second diameter. A mating second ball bearing race is provided. The second ball bearing race extends downwardly from the second circular bearing track and is sized and shaped to fit slidably a series of ball bearings of the second diameter. A series of ball bearings of the second diameter is provided. The series of ball bearings is located between the first and second circular bearing races.
In still a further variant the bearing is either a ball bearing or a roller bearing.
In yet a further variant of the invention, the attaching means is a male thread located at the first end of the axle and the securing means is a washer and a mating threaded locking nut.
In another variant, the attaching means is a transverse hole in the first end of the axle and the securing means is a washer and pin. The pin is sized and shaped to fit frictionally within the transverse hole.
In yet another variant, the watercraft includes an opening. The opening extends from the upper surface of the watercraft into the recess. The opening provides access to the attaching means and the securing means. The opening provides for means for introducing a stream of water into the recess to facilitate the removal of dirt and debris from the bearing and from the first and second circular bearing tracks.
In still another variant, the fin and watercraft system includes a removable sealing plug. The plug is sized and shaped to fit frictionally within the opening.
In a further variant, the system includes a flexible seal. The flexible seal includes a ring. The ring is formed of resilient material and is fixedly attached to the recess of the watercraft. The ring extends from the lower surface of the watercraft upwardly for a first predetermined distance. The ring is sized and shaped to fit slidably about an outer diameter of the circular rotational portion of the fin. When the ring bears against the outer diameter of the circular rotational portion of the fin, a flexible seal will be formed that permits rotation of the fin with respect to the watercraft while controlling the entry of sand and debris into a region of the bearing plate.
In still a further variant of the invention, the means for limiting rotation of the fin with respect to the bearing plate includes a pin. The pin extends vertically from the top surface of the circular rotational portion of the fin for a first predetermined distance. The pin is spaced from the vertical axis of the fin by a second predetermined distance. An arcurate slot is provided. The slot has a first end and a second end and penetrates the bearing plate from its upper surface to its lower surface. The arcurate slot is sized and shaped to slidably fit the pin. The first end of the slot is positioned such that the fin is in either the first position or the third position when the pin is positioned at the first end of the slot. The second end of the slot is positioned such that the fin is in either the second position or the fourth position when the pin is positioned at the second end of the slot.
In still another variant, the fin and watercraft system includes a threaded opening. The opening extends from the first or second side of the watercraft to the nearest recess adjacent the pin. An elongated setscrew is provided. The setscrew is sized and shaped to engage the threaded opening and is of sufficient length to bear against the pin when the fin is in either of the first or third position. When the setscrew is turned inwardly to bear against the pin, the horizontal axis of the fin will be deflected from being parallel to the centerline of the watercraft by an angle of between zero and fifteen degrees.
In still a further variant, the lower surface of the watercraft has a symmetrical V-shaped cross-section.
In a final variant of the invention, the included angle of the V-shaped cross-section is between one hundred fifty degrees and one hundred eighty degrees.
An appreciation of the other aims and objectives of the present invention and an understanding of it may be achieved by referring to the accompanying drawings and the detailed description of a preferred embodiment.